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为了研究不同EGR(废气再缩环)率下后喷时刻对柴油机性能的影响,在一台改造的单缸柴油机上,总循环喷油量固定为每循环50mg,后喷油量为每循环8mg,通过改变EGR率大小和后喷时刻的方法开展了试验研究。研究结果表明:加了后喷之后,缸内峰值压力降低,燃烧相位后移,EGR率较低时放热率峰值略有增高,而EGR率较高时放热率峰值逐渐降低;与无后喷相比,后喷时刻(上止点后)为15℃A和25℃A时,指示热效率降低;EGR率较低,后喷时刻(上止点后)为5℃A时NOx排放有所升高,高EGR率时,后喷时刻对NOx排放几乎没有影响;不同EGR率下,后喷时刻对Soot(碳烟)排放影响不同,主要取决于后喷时的缸内温度;虽然后喷时刻对CO和THC排放影响较小,但在高EGR率下,随后喷时刻推迟,CH4所占比例降低。
In order to study the effect of post-injection timing on diesel engine performance at different EGR rates, the total circulating injection volume was fixed at 50 mg per cycle and the post-injection volume was 8 mg per cycle on a modified single-cylinder diesel engine , By changing the size of EGR rate and post-injection time to carry out the pilot study. The results show that the peak pressure decreases and the combustion phase moves backward when the post-injection is added. The peak value of the heat release rate slightly increases when the EGR rate is low, while the peak value of the heat release rate decreases gradually when the EGR rate is higher. Spray, compared to the post-injection time (top dead center) of 15 ℃ A and 25 ℃ A, indicating lower thermal efficiency; EGR rate is low, post-injection time (top dead center) At high and high EGR rates, post-injection timing has little effect on NOx emissions; post-injection timing has a different effect on Soot emission at different EGR rates, depending on the in-cylinder temperature at post-injection; Moment of CO and THC emissions at any time smaller, but at high EGR rate, followed by the postponement of the moment, CH4 proportion decreased.